Heating elements

ABSTRACT

A water heating element ( 98 ) is disclosed which is in the form of a tube that is open at both ends thereby to form a through passage, wherein the tube comprises a metal outer sleeve and a co-axial metal inner sleeve having an electrically insulating material in the form of ceramic beads or magnesium oxide powder therebetween with electrical resistance wires running through the insulating material. The element ( 98 ) is mounted in an inclined position in the hot water cylinder ( 102 ) with the open lower end of the element close to the bottom wall of the hot water cylinder.

FIELD OF THE INVENTION

THIS INVENTION relates to heating elements specifically, but notexclusively, for heating water.

BACKGROUND TO THE INVENTION

In view of the cost of electricity, it is desirable that heatingelements used to heat the water in hot water cylinders should be asefficient as possible. Desirably, the water should be raised as rapidlyas possible to the temperature set on the thermostat and then theheating elements switched off

The present invention provides a heating element which enables morerapid heating to take place than is possible with heating elements thatare conventionally used to heat the water in hot water cylinders.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the present invention there is provided aheating element in the form of a hollow tube defining a passage, thepassage being open at both ends so that water can flow through the tubefrom an inlet end of the passage to an outlet end of the passage.

Said the tube preferably comprises inner and outer shells with aresistance wire between the shells. In this form said outer shell cancomprise an elongate outer metal sleeve and a cylindrical liner ofelectrically insulating material inside said outer metal sleeve, and theinner shell can comprise an elongate inner metal sleeve and acylindrical sheath of electrically insulating material on the outside ofsaid inner metal sleeve, said resistance wire being in a space betweensaid sheath and said liner. The metal sleeves can be of copper and theliner and sheath can be of ceramic material.

End rings can be provided for closing both ends of said space in whichsaid resistance wire is located.

In another form said tube can comprise an outer metal sleeve and aninner metal sleeve with side-by-side beads between the sleeves, eachbead having a central opening through which said inner metal sleevepasses and a plurality of further openings through which the resistancewire passes.

In yet another form said tube is constituted by an elongate metal sleevewith at least one resistance wire within the sleeve and extending alongit, there being electrically insulating material within the sleeve forelectrically isolating said resistance wire from the sleeve, said sleevebeing wound into the form of a hollow coil with a plurality of turns,said passage being bounded by the turns of the coil.

Adjacent turns of the coil preferably touch one another.

Said passage can have therein a component which reduces the area of thepassage over the length of the component. Preferably said component isat one end of said passage.

According to a further aspect of the present invention there is provideda block for mounting the heater on the mounting plate of a hot watercylinder, an elongate mounting element protruding from said block, theelement having a bend in it so that it has a first portion extendingfrom said block and a second portion which is at an angle to said firstportion, and a water heating structure including a resistance wireconnected to said second portion of said element.

Preferably, when said first portion is horizontal, the second portion isat an angle of 30 to 60 degrees with respect to the horizontal. Saidmounting element can be in the form of a tube and in a specific formsaid mounting element is constituted by a pair of parallel tubes.

The water heater can include a pocket for a thermostat, the pocket beingexternally threaded over an end portion thereof and the mounting blockhaving an internally threaded bore through it into which said pocket canbe screwed.

According to another aspect of the present invention there is providedan installation comprising, in combination, a hot water cylinder havinga mounting plate and a water heater as defined in any one of the threepreceding paragraphs, said block of the water heater being secured tothe mounting plate with said first portion protruding into the cylinderand said second portion and said heating structure extending downwardlyfrom said first portion towards the bottom of the cylinder.

There can be a mounting structure for the heating element, the mountingstructure having a bend in it so that when the mounting structure issecured to a vertical wall of a hot water cylinder, the heating elementslopes down from said wall.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show how thesame may be carried into effect, reference will now be made, by way ofexample, to the accompanying drawings in which:

FIG. 1 is a pictorial view of an assembled hollow heating element inaccordance with the present invention;

FIG. 2 is a view similar to that of FIG. 1 but cut away to reveal theinternal construction;

FIG. 3 illustrates, to a larger scale, the open end of the heatingelement;

FIG. 4 is a view identical to that of FIG. 1 but with components cutaway to further illustrate the internal construction;

FIG. 5 illustrates the end of the heating element which is mounted onthe wall of the hot water cylinder;

FIGS. 6 and 7 are pictorial views of a further embodiment of heatingelement according to the invention;

FIG. 8 is a diagrammatic cut away view of the heating element of FIGS. 6and 7;

FIG. 9 is a pictorial view of a mounting for a heating element;

FIG. 10 is cut away view of another heating element;

FIG. 11 is a pictorial view of a heating element which includes a coil;

FIG. 12 is a diagrammatic representation of another heating element; and

FIG. 13 illustrates a hot water installation.

DETAILED DESCRIPTION OF THE DRAWINGS

The heating element 10 illustrated in FIG. 1 comprises a hollow tube 12and, at one end of the tube 12, a structure 14 for mounting the heatingelement on the wall of a hot water cylinder (not shown).

The tube 12 comprises, see FIGS. 2 to 4, an outer shell 16 and an innershell 18. The shell 16 comprises a cylindrical outer metal sleeve 20,preferably of copper, and a cylindrical liner 22 which is of anelectrically insulating material such as a ceramic. The sleeve 20projects beyond the liner 22 (see FIGS. 2 and 3) at both ends of theelement.

The inner shell 18 comprises an inner metal sleeve 24, preferably ofcopper, and an outer sheath 26 of an electrically insulating materialsuch as a ceramic. The sleeve 24 projects beyond the sheath 26 at bothends (see FIG. 3). There are flanges 28 on the outside of the sheath 26at both ends.

The flanges 28 of the sheath 26 are in contact with the liner 22 therebyto hold the apart those parts of the liner 22 and sheath 26 which arebetween the flanges 28. This provides an elongate cavity for a woundresistance wire 30 which is wound onto the sheath 26 between the flanges28.

A metal end ring 32 fits onto the sleeves 20 and 24 at the open end ofthe element 10 and prevents water entering the cavity which contains theresistance wire 30. The end ring 32 can be brazed to both of the sleeves20 and 24.

An end ring 34 (see FIG. 5), similar to the end ring 32, fits onto thesleeves 20 and 24 to prevent water entering the other end of the cavityin which the wound resistance wire 30 is contained.

The ring 34 has openings 36 in it for enabling electrical leads 38 to bepassed through it and connected to the resistance wire 30.

Three short copper pipes are shown at 40.

The mounting structure 14 comprises a block 42 having a cylindricalexternally threaded section 44. This section screws into the mountingplate (not shown) of the hot water cylinder with the imposition ofsuitable water seals.

Two through bores 46, 48 in the block 42 allow the electrical leads 38which are connected to the resistance wire 30 to pass through the block42 and enter the bores in the ring 34. A further bore 50 in the block 42receives a one-way valve (not shown).

At one end each pipe 40 is welded or otherwise secured to the block 42in alignment with the bores 46, 48 and 50. The other end of each pipe 40passes through a respective one of the openings 36 in the ring 34 and iswelded or otherwise secured to the tube 12. Conveniently, the pipes 40are secured to the sleeve 24 but they can be secured to the sleeve 20.The leads 38 pass through two of the pipes 40 and the bore 50communicates with the pipe 40. It is also possible to secure the pipes40 to the metal cap 34 and then secure the cap 34 to the sleeve 20. Thepipes 40 form the mechanical connection between the block 42 and thetube 12.

If desired the pressure in the cavity in which the heating coil 30 islocated can be increased to above atmospheric or, alternatively, theatmospheric air can be replaced by another gas such as helium using thevalve in the bore 50.

In use, when current is flowing, hot water layers form on both the innerand outer metal sleeves 20 and 24. Heating of the water inside the innermetal sleeve 20 causes a flow of water through the hollow interior ofthe tube 12 which, as best seen in FIGS. 1 and 5, is open at both ends.

Turning now to FIGS. 6 to 8, these illustrate an embodiment which hasparts in common with the embodiment of FIGS. 1 to 5. Like parts havebeen designated with the same reference numerals to which the suffix “1”has been added.

The liner 22 and sheath 26 are replaced by a row of what in the industryare called “beads”. Each bead, designated 52, has a central opening anda plurality of further openings which receive the resistance wires.

In the embodiment of FIGS. 6 to 8, the array of beads 52 is pushed intothe outer sleeve 24.1 (from the left hand end in FIG. 8) until itencounters a ring 54 of electrically insulating material which isbetween the metal ring 32.1 and the beads.

A second insulating ring 56 is pushed into the sleeve 24 to insulate theresistance wires from the metal end cap 34.1.

The inner metal sleeve 24.1 is pushed into the central opening of thearray of beads 52. The array of beads thus replaces the liner 22 and thesheath 26, and the beads lie between the sleeve 20.1 and the sleeve24.1.

The mounting 58 shown in FIG. 9 includes a block 60 and an externallythreaded section 62. The face of the block 60 remote from the section 62has a groove 64 in it for receiving a sealing ring, such as a 0-ring.

The bores of the block 60 equivalent to the bores 46, 48 of the block 42are extended by hollow bosses 66, 68 which receive plugs 70, 72 ofelectrically insulating material. Bores 74, 76 are provided in the plugs70, 72. The valve referred to above as being in the bore 50 of the block42 is shown at 78. A blind tapped bore at the centre of the block 60 isdesignated 80.

The mounting 58 can be used in two ways. It can be screwed into thefixed mounting plate of the hot water cylinder as described above withreference to the block 42. Alternatively the face of the block with the0-ring groove in it can be pressed against the inside face of aremovable mounting plate. A stud or bolt (not shown) is passed through ahole in the mounting plate and screwed into the tapped bore 80. Thissecures the mounting and hence the entire heating element to themounting plate. The tube 12 is inserted into the interior of the hotwater cylinder until the mounting plate comes into contact with theexternal surface of the cylinder. The mounting plate is then bolted tothe cylinder.

Holes in the mounting plate permit access to the bosses 66, 68 and tothe valve 78.

The heating element of this FIG. 10 has many components in common withthose of the preceding Figures and where applicable like parts have beendesignated with the same numerals.

A component designated 82 is fitted into one end of the inner sleeve 24.The component 82 is in the form of a plug which has a cylindrical part84 which slides into the sleeve 24 and a flange 86 which abuts the endof the sleeve 24. The bore 88 in the component 82 is of smaller diameterthan the internal diameter of the sleeve 24. The component 82 thusconstitutes a flow restrictor. Flow into the passageway is through therestricted bore of the component 82.

In another embodiment (not shown) the flange 86 is omitted and thecylindrical part 84 is pushed into the end of the sleeve 24. The bore inthe part 84 can taper from each end to a constricted throat between theends.

The hollow heating elements described above can be sheathed in heatinsulating material. Heating then takes place substantially entirelywithin the passageway through the element. This causes a flow of waterthrough the passageway that exerts an axial thrust on the heatingelement.

In FIG. 11 the heating element 90 initially comprises an elongate,straight copper tube 92 which has in it beads through holes in whichresistance wires pass. In an alternative form the tube 92 is filled withmagnesium oxide powder through which the wires pass. The powderelectrically isolates the wires from the tube and from one another.

The tube 92 is then wound into the form of a coil with adjacent turnstouching one another. This ensures that water in the hollow coil cannotescape between adjacent turns but must flow the full length of the coil.

In FIG. 12 the heating element is designated 98 and is connected by twohollow mounting tubes 100 to the block designated 42. Each mounting tube100 has a bend in it so that when the block 42 is secured to thevertical mounting plate (not shown in FIG. 12) the element 98 slopesdownwardly at an angle of between 30° and 60° to the horizontal. Thepreferred angle is between 40° and 50° with respect to horizontal andexperimental work has shown that an angle of 45° with respect tohorizontal gives the best results.

Cold water near the bottom of the cylinder is drawn into the hollowelement 98, is heated in the sloping passage within the element 98 andemerges as a hot water stream from the upper end of the passage in theheating element, thus creating a convection flow in the cylinder.

The element 98 can be of any of the forms above with reference to FIGS.1 to 11.

FIG. 13 shows a hot water installation comprising a thermally insulatedcylinder 102, a cold water inlet 104 and a hot water outlet 106. Theelement 98 is mounted on the end wall 108 of the cylinder 102. The openlower end of the element 98 is close to the lowermost part of thecylinder 102. A pocket 110 is provided for receiving a thermostat.

1. A heating element in the form of a hollow tube defining a passage,the passage being open at both ends so that water can flow through thetube from an inlet end of the passage to an outlet end of the passage.2. A heating element as claimed in claim 1, wherein the tube comprisesinner and outer shells with a resistance wire between the shells.
 3. Aheating element as claimed in claim 2, wherein said outer shellcomprises an elongate outer metal sleeve and a cylindrical liner ofelectrically insulating material inside said outer metal sleeve, and theinner shell comprises an elongate inner metal sleeve and a cylindricalsheath of electrically insulating material on the outside of said innermetal sleeve, said resistance wire being in a space between said sheathand said liner.
 4. A heating element as claimed in claim 3, wherein themetal sleeves are of copper and the liner and sheath are of ceramicmaterial.
 5. A heating element as claimed in claim 3 and including endrings for closing both ends of said space in which said resistance wireis located.
 6. A heating element as claimed in claim 1 and including, atone end of the tube, a structure for mounting the tube on the wall of ahot water cylinder, the structure including passageways for electricalleads connected to said resistance wire.
 7. A heating element as claimedin claim 6, wherein said structure includes a block having bores throughit, said bores constituting the passageways for said leads.
 8. A heatingelement as claimed in claim 7, and including metal tubes secured to saidblock and to one or other or both of said sleeves, said leads passingthrough said tubes.
 9. A heating element as claimed in claim 1, whereinsaid tube comprises an outer metal sleeve and an inner metal sleeve withside-by-side beads between the sleeves, each bead having a centralopening through which said inner metal sleeve passes and a plurality offurther openings through which the resistance wire passes.
 10. A heatingelement as claimed in claim 1, wherein said tube is constituted by anelongate metal sleeve with at least one resistance wire within thesleeve and extending along it, there being electrically insulatingmaterial within the sleeve for electrically isolating said resistancewire from the sleeve, said sleeve being wound into the form of a hollowcoil with a plurality of turns, said passage being bounded by the turnsof the coil.
 11. A heating element as claimed in claim 10, whereinadjacent turns of the coil touch one another.
 12. A heating element asclaimed in claim 1, in which the passage has therein a component whichreduces the area of the passage over the length of the component.
 13. Aheating element as claimed in claim 12, wherein said component is at oneend of said passage.
 14. A water heater comprising a block for mountingthe heater on the mounting plate of a hot water cylinder, an elongatemounting element protruding from said block, the element having a bendin it so that it has a first portion extending from said block and asecond portion which is at an angle to said first portion, and a waterheating structure including a resistance wire connected to said secondportion of said element.
 15. A water heater as claimed in claim 14,wherein, when said first portion is horizontal, the second portion is atan angle of 30 to 60 degrees with respect to the horizontal.
 16. A waterheater as claimed in claim 15, wherein said angle is between 40 and 50degrees.
 17. A water heater as claimed in claim 14, wherein said elementis in the form of a tube.
 18. A water heater as claimed in claim 14,wherein said element is constituted by a pair of parallel tubes.
 19. Awater heater as claimed in claim 17, wherein electrical leads extendthrough said tube or tubes and are connected to said resistance wire.20. A water heater as claimed in claim 14, and including a pocket for athermostat, the pocket being externally threaded over an end portionthereof and the mounting block having an internally threaded borethrough it into which said pocket can be screwed.
 21. A water heater asclaimed in claim 20, wherein said pocket is above said first portion.22. An installation comprising, in combination, a hot water cylinderhaving a mounting plate and a water heater as claimed in claim 14, saidblock of the water heater being secured to the mounting plate with saidfirst portion protruding into the cylinder and said second portion andsaid heating structure extending downwardly from said first portiontowards the bottom of the cylinder.
 23. A heating element as claimed inclaim 1 and including a mounting structure for the heating element, themounting structure having a bend in it so that when the mountingstructure is secured to a vertical wall of a hot water cylinder, theheating element slopes down from said wall.